The present invention concerns a method of and an apparatus for cooling of a motor for driving an aircraft wheel. More particularly, but not exclusively, this invention concerns an aircraft comprising a landing gear assembly having a motor for driving a wheel of the landing gear assembly, wherein the motor requires cooling. The invention also concerns a method of cooling a motor that is being used to drive a landing gear wheel of an aircraft landing gear assembly of an aircraft during taxiing manoeuvres of the aircraft.
Aircraft are required to taxi on the ground, for example between locations on airfields. For example, a commercial passenger aircraft is required to taxi between a runway at an airport and the location at the airport (e.g. a terminal having a departures/arrivals gate) at which the aircraft's passengers are to board or disembark the aircraft. In the prior art, such taxiing has typically been performed by using the thrust from the aircraft's engines to propel the aircraft forwards, so that the wheels on landing gear assemblies of the aircraft are caused to rotate. Since ground taxi speeds are necessarily relatively low, the engines must be run at a very low power. This may mean that there is relatively high fuel consumption as a result of the poor propulsion efficiency at this low power. This can lead to an increased level of both atmospheric and noise pollution locally around airports. Moreover, even when the engines are run at low power it is generally necessary to apply the wheel brakes to limit ground taxi speeds, leading to a high degree of brake wear.
Reversing of a civil aircraft, for example away from a terminal gate, using its main engines is not permitted. When reversing is necessary, or in other situations where ground taxiing via main engine thrust is not practicable, tow trucks are used to manoeuvre aircraft around. This process is laborious and costly.
It has therefore been proposed that a separate drive system be provided to power the wheels of an aircraft landing gear during ground taxi operations. Such proposed separate drive systems comprise a motor mounted locally to the wheel of a landing gear assembly, typically a hydraulic or electric motor. Torque is provided to the wheel from the motor. Such proposed separate drive systems are referred to as autonomous ground taxi systems and sometimes as e-taxi (electric taxi) systems.
One example is disclosed in US2006/0065779, which proposes a nose aircraft wheel system powered by electric power from an auxiliary power unit (APU) on the aircraft. Another prior art arrangement which is not restricted to nose landing gears is described in WO2011/023505.
For an additional drive system locally mounted on a landing gear assembly to be of benefit it needs to be lightweight, yet able to withstand the harsh conditions that are encountered in the region of a landing gear assembly when the wheels are in contact with the ground. The addition of a drive system on a landing gear assembly should not affect detrimentally the other functions of the landing gear assembly, such as the process of the landing gear moving between deployed and stowed positions and/or such as the braking function provided by the wheel brakes. Safety cannot be compromised.
A motor of an e-taxi/autonomous ground taxi drive system may require cooling in order for it to operate efficiently and safely. Air cooling of a motor may offer a simple means of cooling the motor. Heat exchanging fins may be provided to facilitate cooling of the motor by means of air passing over the fins extracting and carrying away heat as the landing gear assembly moves through ambient air when the aircraft travels relative to the ground. It is believed however that dust, debris and other dirt and unwanted flatter might clog up the fins, thus requiring regular cleaning in order for their effectiveness to be maintained. It has been proposed that fans be provided to assist with cooling and that such fans may be powerful enough to keep the fins clear of debris. The use of high-power fans adds extra mass and may add extra complexity.
US2013/284854 proposes a wheel-mounted e-taxi motor pre-cooled by means of producing airflow through the rotors of the drive motor.
An alternative way in which to cool a motor is by means of liquid cooling. However, the extra mass that would be needed in order to provide a dedicated liquid based cooling system for one or more e-taxi motors is likely to make such an alternative unattractive.
The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method, and/or apparatus, for cooling a motor for driving a landing gear wheel on an aircraft. Alternatively or additionally, the present invention seeks to provide an improved method and and/or apparatus for performing aircraft taxiing manoeuvres.